Snowmobiles have been known for many years. Early snowmobiles were developed with an appearance that is very primitive compared to the snowmobile of today. The snowmobile of modern times is a sophisticated vehicle with heated handle bars, twin head lights, a reversible transmission and many other improvements not found in the original snowmobiles. One of the developments of recent times has been the very high powered engines. Today the engines found in snowmobiles may rival the engines in high powered race cars of a few years ago. Snowmobile engines of three hundred horse power are not uncommon.
One of the weak points in snowmobiles has been the drive system. Snowmobile drive systems have generally included a chain rpm reduction drive. The rpm of the engine must be reduced prior to applying the rotational drive to the differential sprockets driving the track. In the past the drive system has included a chain and sprocket system. The chain and sprocket system tends to wear and is subject to extreme abuse in the activities of normal snowmobile use. The rapid starts and stops, the very high rpm torque when the snowmobile leaves the ground and leaps into the air results in extremely rapid changes of speed and load. The chain will typically last three or four hundred hours.
There have been longstanding needs for a snowmobile drive system that is durable, lightweight, minimal number of parts, minimal number of moving parts, compact and of reduced shaft wind-up. Each of these longstanding needs is explained further below.
There has been a longstanding need for a drive system that is more durable than the chain and sprocket system. The present invention replaces the chain and sprocket system that has been the standard in the past snowmobiles with a system that withstands torques far in excess of those encountered in snowmobiles in the past. The present invention provides a drive system that will last for up to fifteen hundred hours of rugged operation. When replacement becomes necessary the drive system of the present invention is easily replaced.
There has also been a longstanding need to reduce the weight of snowmobiles. A lower weight snowmobile has the ability to accelerate more quickly and is much easier to maneuver. The prior art chain and sprocket drive trains require the use of three axes. Specifically, the prior art chain and sprocket drive trains include the engine drive shaft, a continuously variable transmission extending from the engine drive shaft to a second shaft and a chain and sprocket gear reduction from the second shaft to a third shaft. The third shaft includes sprockets for driving the continuous track that drives the snowmobile forward in the snow. Each shaft and corresponding parts such as support brackets and bearings add weight to the drive train. It is highly desirable to reduce the number of parts to reduce the weight of the snowmobile.
There has additionally been a longstanding need to reduce the number of moving parts. Moving parts tend to wear out and require time and money for repair and replacement.
Moving parts such as a rotating shaft also lower the energy efficiency of a drive train.
There has additionally been a longstanding need to design a drive train that is more compact so as to take up less space within the snowmobile.
There has additionally been a longstanding need for a drive train that reduces shaft wind-up (lag in torque across length of a member) by eliminating the additional shaft necessitated by the use of a chain and sprocket reduction drive.